This invention relates generally to media handling systems for inkjet printing devices, and more particularly to a media handling system which carries a media sheet along an endless loop belt.
Inkjet printing devices eject ink drops onto a media sheet from a plurality of nozzles. The ink drops form symbols, characters or graphics as desired. Placement of the drops is important for achieving desired print quality and resolution. To achieve accurate dot placement, the timing of each nozzle ejection is precisely controlled relative to the position of the media sheet. The media sheet is carried along a media path and passed through a print zone where ink drops are ejected onto the media sheet. To achieve accurate dot placement the motion of the media sheet is to be accurately controlled.
In conventional media handling systems, the media sheet is either stepped or continuously advanced. In a stepping embodiment, one or more rows of dots are printed at a time onto the media sheet while the media sheet is stationary. This occurs, for example, as an inkjet printhead is scanned across the media sheet. Alternatively, this occurs while a page wide array of inkjet nozzles ejects ink drops. Upon completion of printing to the one or more rows, the media sheet is advanced a known media advance distance. Another one or more rows of dots then are printed. For embodiments in which the media sheet is continuously advanced, the media sheet is moving while the inkjet printhead is scanning across the media sheet. For either approach, dot placement accuracy is affected by media advance accuracy.
This invention is directed toward a method and apparatus for improving media advance accuracy in a belt driven media handling subsystem for an inkjet printing apparatus.